The properties of synthetically prepared calcium phosphates of biological interest are being studied with a variety of ultrastructural and physical-chemical techniques such as electron microscopy, x-ray diffraction, extended x-ray absorption fine structure analysis, B-E-T surface area methods, and standard analytical chemistry procedures. Topics under current investigation include (1) the local structure about Ca++ ions in crystalline and amorphous calcium phosphates (2) the preparation and characterization of synthetic analogues to intracellular mineral deposits such as occur in mitochondria and in subcellular storage organelles, and (3) the formation and properties of precipitates induced in phosphate solutions by the ionophoric translocation of Ca++ across bulk organic solvent barriers.